There have been techniques called as “augmented reality” or “mixed reality” for displaying a virtual image overlapped with the real world. Some of those techniques have been in practical use (see, for example, Non-patent document 1). Those techniques can be roughly classified into optical see-through (see, for example, Patent document 1) and video see-through (see, for example, Patent document 2) based on method of displaying the augmented reality.
FIG. 16 is a schematic for explaining the optical see-through. In the optical see-through, as shown in FIG. 16, using a semitransparent display panel 401, the optical see-through causes an observer OBS to visually recognize an overlapped image of a virtual image VI and a background BG. The virtual image VI being an image electronically displayed on the semitransparent display panel 401, and the background BG being the real world viewed through the semitransparent display panel 401.
FIG. 17 is a schematic for explaining the video see-through. In the video see-through, as shown in FIG. 17, using a wearable head-mounted display, a CAVE system, or the like, the virtual image VI is electronically combined with a background image of the real world shot by a camera 501, and the combined image is displayed.
Patent document 1: Japanese Patent Application Laid-open No. H11-174367
Patent document 2: Japanese Patent Application Laid-open No. 2001-92995
Non-patent document 1: “Mixed reality”, by Takaaki Endo et al., in OPTRONICS (2002) No. 2, pages 137 to 141